Unit 4 - Immune System K-M

Question 1

Adaptive Immunity creates…

Answer 1

antigen-specific responses
- adaptive immune responses are ANTIGEN-SPECIFIC EVENTS in which the body recognizes a particular foreign substance & selectively reacts to it

Question 2

Adaptive Immunity

Basic Steps of PRIMARY Response/Exposure:

Answer 2

1. Naïve T and B LYMPHOCYTES exposed to antigen for first time (first exposure)
2. Clonal expansion occurs (mitosis of B-cells and T-cells that have BCRs/TCRs specific for the antigen)
3. Differentiate into effector cells and memory cells.
   Effector B-cells = Plasma cells.
   Effector T-cells = Helper T cells and Cytotoxic T-Cells
4. Plasma B cells produce antibodies, Memory B cells remain in circulation (humoral immunity).

Question 3

Naïve T and B lymphocytes

Answer 3

at birth, each clone of lymphocytes is represented by only a few cells, called native lymphocytes

Question 4

Clonal expansion

Answer 4

b/c the small # of cells in each naive clone isn’t enough to fight off foreign invaders, the 1st exposure to an antigen activates the appro. clone & stimulates it to cells in the clone

• this process (clonal expansion), creates add. cells in the clone
• naive cells continue to be generated throughout an individual’s lifetime

Question 5

Effector cells

Answer 5

carry out the immediate response & then die within a few days

Question 6

Memory cells

Answer 6

long-lived & continue reproducing themselves

Question 7

Effector B-cells =

Answer 7

Plasma cells

Question 8

Effector T-cells =

Answer 8

Helper T cells and Cytotoxic T-Cells

Question 9

Plasma B cells

Answer 9

produce antibodies

- to create humoral immunity, the soluble antibodies of the plasma

Question 10

Memory B cells

Answer 10

remain in circulation (humoral immunity)

- stay alive, waiting for the next exposure to the same antigen

Question 11

Antibody production is _____ & ______ in magnitude in the primary immune response b/c _______

Answer 11

SLOWER

LOWER

the body has not encountered the antigen before

Question 12

Adaptive Immunity

Basic Steps of SECONDARY Response/Exposure: (Immune Memory)

is _____ & ______ b/c _______

Answer 12

QUICKER

LARGER

of the memory B cells that remained behind after the 1st exposure

Question 13

Adaptive Immunity

Basic Steps of SECONDARY Response/Exposure: (Immune Memory)

Answer 13

1. Many MEMORY T and B LYMPHOCYTES in circulation are exposed to same antigen that initiated their formation.
2. Clonal expansion occurs more quickly (there is a larger population of memory T and B cells for the specific antigen than there was for Naïve T and B cells during the first exposure).
3. Increased number of effector T and B cells and memory T and B cells are formed.
4. More plasma cells, results in increased antibody production compared to primary response. More cytotoxic cells allows for faster more effective destruction of infected host cells.
5. Overall more cells = more response to 2nd exposure

Question 14

Adaptive Immunity – Cell Mediated Immunity

Answer 14

Effective against virus infected cells and cancerous cells

Question 15

Adaptive Immunity – Cell Mediated Immunity

Steps for secondary response:

Answer 15

1. Pathogen invades tissues
2. Phagocytosis by resident macrophage or dendritic cell.
3. Antigen presentation to TYPE 1 Helper T-cells (CD4+) by binding of TCR to antigen-MHC-II.
4. Activated Type 1 Helper T cells secrete IL-2 (cytokine) which activates Cytotoxic T-Lymphocytes (CD8+)
5. Cytotoxic T-Lymphocyte TCRs bind to antigen-MHC-I complexes on infected host cells.
6. Cytotoxic T-Lymphocytes release perforin onto infected host cell membrane, creating a pore.
7. Cytotoxic T-Lymphocytes release granzymes into infected host cell which will digest the cell.
8. Infected host cell undergoes apoptosis (lysis).

Question 16

Steps for primary response would be similar (to secondary response for CELL MEDIATED IMMUNITY), but would involve…

Answer 16

antigen presentation to Naïve T cells followed by clonal expansion in between step 2 and 3

Question 17

Adaptive Immunity – Humoral Immunity

Answer 17

Antibody mediated immunity.

Question 18

Adaptive Immunity – Humoral Immunity

Steps for secondary response:

Answer 18

1. Pathogen invades tissues
2. Pathogen recognized by TLRs (Toll like-receptors) or opsonized by complement or antibodies.
3. Phagocytosis of pathogen by resident macrophage or dendritic cell.
4. Antigen presentation to TYPE 2 Helper T-cells (CD4+) by binding of TCR to antigen-MHC-II.
5. Activated TYPE 2 Helper T cells secrete IL-4, IL-5, IL-6 (cytokines) which activate B-cells to proliferate (clonal expansion) and Plasma cells to produce antibodies.
6. Antibodies facilitate:
   a. phagocytosis (e.g. act as opsonins)
   b. cell lysis (apoptosis) via activation of classical complement pathway or
   activating degranulation of NKCs and/or eosinophils
   c. Facilitate production of more antibodies (though action on B cells)

Question 19

Adaptive Immunity – Humoral Immunity

6. Antibodies facilitate:

Answer 19

a. phagocytosis (e.g. act as opsonins)
b. cell lysis (apoptosis) via activation of classical complement pathway or activating degranulation of NKCs and/or eosinophils
c. Facilitate production of more antibodies (though action on B cells)

Question 20

Steps for primary response would be similar (to secondary response for HUMORAL IMMUNITY), but would involve…

Answer 20

antigen presentation to Naïve B cells followed by clonal expansion in between steps 3 and 4

Question 21

Adaptive Immunity – Humoral Immunity

Two categories of humoral immunity:

Answer 21

1. Active Immunity
   a. Natural
   b. Artificial
2. Passive Immunity
   a. Natural
   b. Artificial

Question 22

Adaptive Immunity – Humoral Immunity

1. Active Immunity

Answer 22

body is exposed to the pathogen and produces its own antibodies via humoral immune response

Question 23

Adaptive Immunity – Humoral Immunity

1. Active Immunity
   a. Natural

Answer 23

pathogen infects body through natural means (crosses barriers, evades innate immune system and triggers a normal humoral immune response that leads to the production of antibodies. Person becomes ill and then recovers.

Question 24

Adaptive Immunity – Humoral Immunity

1. Active Immunity
   b. Artificial

Answer 24

Vaccination:

i. Vaccines mimic the pathogen. Can be composed of:
- Attenuated or killed pathogen
- Purified macromolecules
- DNA
All cause slow primary responses, which makes them harmless (mild symptoms at worst)

ii. Fake pathogen triggers creation of antibodies and memory cells (long-term immunity)

iii. Subsequent exposure to real pathogen (the memory cells) produces fast and more effective secondary response.
i. e. vaxxed person is later infected by the pathogen

Question 25

Vaccination

Answer 25

containing dead or disabled pathogens or their products

existence of a secondary immune response is what allows vaccinations to be an effective protection from disease

Question 26

Vaccines

Answer 26

contain an altered pathogen that no longer harms the host but that can be recog. as foreign by immune cells

Question 27

Adaptive Immunity – Humoral Immunity

2. Passive Immunity

Answer 27

the body acquires antibodies that were made by another individual or organism (often horses, sheep).

Question 28

Adaptive Immunity – Humoral Immunity

2. Passive Immunity
   a. Natural

Answer 28

e.g. the antibodies that pass from mother to fetus across the placenta or through breast milk.

Question 29

Adaptive Immunity – Humoral Immunity

2. Passive Immunity
   b. Artificial

Answer 29

injections that contain antibodies (antiserums) as opposed to attenuated pathogen.

• E.g.1: antivenin for snake bites
• E.g.2: convalescent serum for treatment of severe COVID-19 or ebola. Convalescent serum is produced by taking antibodies from a recovered person, and injecting them into someone who is ill to boost their immune response.
• E.g. 3: used for post-exposure injections for several conditions like rabies, tetanus, and Hepatitis B (if the person was exposed and had not been vaccinated).